President Barack Obama took aim at his presumptive opponent's newly-picked running mate Monday, accusing him of opposing legislation that would help drought-battered farmers in the country's Midwest.

Speaking in Council Bluffs, Iowa, the first stop on a three-day, seven-city tour of the Midwestern state, Obama said Wisconsin Congressman Paul Ryan, the presumptive Republican vice-presidential nominee, was among congressional Republican leaders "standing in the way" of the 2012 Farm Bill, which includes disaster aid programs.

"So if you happen to see Congressman Ryan, tell him how important this farm bill is to Iowa and our rural communities," he said. "It's time to put politics aside and pass it right away."

The Obama administration announced Monday that the federal government will purchase up to $170 million worth of meat and fish, the second initiative this month aimed at helping farmers and ranchers affected by the drought. The food purchases will go toward food banks and other nutrition assistance programs.

Last week, the U.S. Department of Agriculture announced it will provide millions of dollars in assistance to restore livestock lands affected by the drought.

Ryan is also campaigning in Iowa, while presumptive Republican U.S. presidential candidate Mitt Romney is campaigning in the southern state of Florida.

The two campaigned Sunday in North Carolina and then in Ryan's home state of Wisconsin. Both states are considered key battlegrounds in the race for the White House.

Ryan told cheering supporters: "We can get this country back on track. We can get our people back to work. We can get our debt paid off so we can give our children a better standard of life."

President Obama, speaking at a campaign fundraiser in his hometown of Chicago on Sunday, called Ryan a "decent man" and a "family man" who is "an articulate spokesman for Governor Romney's vision" - a vision the president said he "fundamentally" disagrees with.

Obama said Romney and Ryan believe getting rid of regulations on big corporations and giving tax breaks to the wealthiest Americans "will lead to jobs and prosperity for everybody else." He called this "trickle-down fairy dust" that has not worked in the past.

Romney is hoping Ryan's work in Congress to cut spending and create smaller government will help energize the Republican Party's conservative base.